A study by a bank compared the average savings of customers who were depositors for
three years or less with those who had been depositors for more than three years. The
results of a sample are:
To test that the two groups of customers have equal savings rates, what is the critical
value of z using α = 0.05?
A university has 1,000 computers available for students to use. Each computer has a
250-gigabyte hard drive. The university wants to estimate the space occupied on the
hard drives. A random sample of 100 computers showed a mean of 115 gigabytes used
with a standard deviation of 20 gigabytes. What is the probability that a sample mean is
between 111 and 119 gigabytes?
The following frequency distribution shows the distribution of delivery times (in days)
for swimstuff.com customer orders during the last month.
What is the relative frequency for orders delivered in less than three days?
For a contingency table test of independence, the formula to compute the degrees of
freedom is __________________________________.
Given the sample information in the following table regarding public opinion on gun
control, who is more likely to favor gun control?
In a negatively skewed distribution, the coefficient of skewness is ______________.
A sample of 500 part-time students revealed that their annual incomes were normally
distributed with a mean income of $30,000 and a standard deviation of $3,000. The
number of students that earned between $27,000 and $33,000 is _____.
In the sampling distribution of the sample means, the standard error of the mean will
vary according to the size of the sample. As the sample size n gets larger, the variability
of the sampling distribution of the means gets _____________.
The manager of a restaurant measures several variables important to quality. These
include food temperature, time to complete an order, and number of times a server visits
a table. These variables are graphed over time. Is this an example of acceptance
sampling or statistical process control?
A company compared the variance of salaries for employees who have been employed
for 5 years or less with employees who have been employed for 10 years or more. They
randomly selected 21 employees with 5 years or less experience and 15 employees with
10 years or more experience. The standard deviation for the group with 5 years or less
experience was $2,225; the standard deviation for the group with 10 years or more
experience was $1,875. Using the 0.05 significance level, what is the F critical value
for the hypothesis test?